Author's personal copy Ecological Modelling 221 (2010) 1674–1686 Contents lists available at ScienceDirect Ecological Modelling journal homepage: www.elsevier.com/locate/ecolmodel Modeling the dynamic habitat and breeding population of Southwestern Willow Flycatcher James R. Hatten a,∗ , Eben H. Paxton b , Mark K. Sogge c a Research Geographer, U.S. Geological Survey, Western Fisheries Research Center, Columbia River Research Laboratory, Seattle, WA 98115, United States b U.S. Geological Survey, Southwest Biological Science Center, Flagstaff, AZ 86001, United States c U.S. Geological Survey, Western Regional Office, Seattle, WA 98104, United States article info Article history: Received 8 June 2009 Received in revised form 17 March 2010 Accepted 30 March 2010 Available online 29 April 2010 Keywords: Change detection Dynamic riparian vegetation GIS Predicted habitat Reservoir management Spatially explicit Southwestern Willow Flycatcher Population dynamics abstract To aid in the management and conservation of Southwestern Willow Flycatcher (Empidonax traillii extimus, hereafter “Flycatcher”), we developed numerous models of flycatcher breeding habitat at Roo- sevelt Lake, AZ. For model development and testing, we compiled 10 years of flycatcher territory data that were obtained from intensive fieldwork between 1996 and 2005. We identified riparian vegetation annually in the project area from Landsat Thematic Mapper images, and extracted floodplain features from a digital elevation model. We created a novel class of temporal (i.e., multiyear) variables by char- acterizing the stability and variability in breeding habitat over a 6-year time interval. We used logistic regression to determine associations between environmental variables and flycatcher territory occur- rence, and to test specific hypotheses. We mapped the probability of territory occurrence with a GIS and determined model accuracies with a classification table and a 10-year population database. Envi- ronmental features that were associated with breeding flycatchers included floodplain size, proximity to water, and the density, heterogeneity, age and stability of riparian vegetation. Our best model explained 79% of the variability in the flycatcher breeding population at Roosevelt Lake. The majority of predicted flycatcher habitat formed between 1996 and 2004 on an exposed lakebed ∼3 years after water levels receded during a prolonged drought. A high correlation between annual reservoir levels and predicted breeding habitat (r = -0.82) indicates that we can create and manage habitat for conservation purposes. Our predictive models quantify and assess the relative quality of flycatcher breeding habitat remotely, and can be used to evaluate the effectiveness of habitat restoration activities. Numerous techniques we developed can be used to characterize riparian vegetation and patch dynamics directly off of satellite imagery, thereby increasing its utility for conservation purposes. Published by Elsevier B.V. 1. Introduction Riparian habitats in the southwestern United States are dis- proportionately important for wildlife. For example, over 50% of Southwestern birds are directly dependent on riparian habitat while it only covers about 1% of the landscape (Knopf et al., 1988; Skagen et al., 1998). Unfortunately, riparian habitat has declined by as much as 90% in historic times, and is generally considered a habitat of great conservation and management concern (Busch and Smith, 1995; Comer et al., 2003; Turner et al., 2003; Rich et al., 2004). Many stressors have contributed to the decline of riparian habitat, but one of the most wide-scale stressors to riparian sys- tems is due to dams (Graf, 2006). Dams disrupt the natural flood cycle that riparian systems have adapted to, creating rivers that flood infrequently, lose their meanders, and generally become more ∗ Corresponding author. Tel.: +1 509 538 2299x252; fax: +1 509 538 2843. E-mail address: jhatten@usgs.gov (J.R. Hatten). channelized (Graf, 2006; Webb and Leake, 2006). However, while much attention has been directed at the down-stream effects of dams, reservoirs can allow for rich riparian habitat to exist along their up-stream fringes. In the U.S. Southwest, many reservoirs fluc- tuate depending on regional patterns of precipitation, and given the right geomorphology of a reservoir basin, large tracts of riparian habitat can form in the reservoir beds and fringes, especially near inflows. Lowering reservoir levels expose soil that is rich in nutri- ents, cleansed of salts, and free of existing vegetation that allows for rapid growth of riparian vegetation. Conversely, rising reservoir levels destroy this habitat, setting the stage for a repeat during the next drawdown. The cycle of creation–destruction caused by fluctuating reser- voir levels, reminiscent of the once-frequent scouring flood events of major rivers in pre-dam times, can create large swaths of dense riparian habitat at relatively young successional stages. When this occurs, the riparian habitat is quickly colonized by wildlife, par- ticularly vagile species such as birds, and can become important habitat for the period of time that it exists. One species of great 0304-3800/$ – see front matter. Published by Elsevier B.V. doi:10.1016/j.ecolmodel.2010.03.026